There is disclosed a solid-state imaging device which includes a plurality of photoelectric converting portions, each having a photosensitive region which generates a charge according to incidence of light, and which has a planar shape of a nearly rectangular shape formed by two long sides and two short sides, and an electric potential gradient forming region which forms an electric potential gradient increasing along a predetermined direction parallel to the long sides forming the planar shape of the photosensitive region with respect to the photosensitive region, the plurality of photoelectric converting portions being juxtaposed along a direction intersecting with the predetermined direction, and a plurality of charge accumulating portions, each being arranged corresponding to the photoelectric converting portion and on the side of the other short side forming the planar shape of the photosensitive region, and each accumulating a charge generated in the photosensitive region of the corresponding photoelectric converting portion (for example, refer to Patent Literature 1). The solid-state imaging device of this type has been used heretofore in various uses, and has been commonly used, particularly, as a light detecting means of a spectroscope.